I. Field of the Invention
The present invention relates generally to attachments for vertical mills.
II. Decription of the Prior Art
Vertical mills are conventionally used in machine shops for vertical milling and drilling operations. Such vertical mills typically comprise a work table on which the work is clamped. The work table, furthermore, is movable both laterally and vertically.
A column above the table supports a quill which is vertically slidably movable with respect to the column. A spindle is rotatably mounted within the quill and is adapted to clampingly engage the driveshaft at one end of a milling cutter. Consequently, upon activation of the vertical mill, the spindle rotatably drives the milling cutter around a substantially vertical axis. The cutting operation is then done by adjusting the position of the work table and/or the vertical position of the quill.
Prior to the actual machining operation, it is a common practice for many machinists to first machine a flat vertical surface along one side of the workpiece. This flat surface is then used as a reference surface for the remaining machining operations on the workpiece.
In order to machine a flat reference surface on one side of the workpiece, it has been the previously known practice to attach an end mill to the spindle and then make multiple machining passes along one side of the workpiece until a flat surface is obtained.
There are, however, a number of disadvantages to this previously known method for machining a flat vertical surface on the workpiece.
One difficulty encountered in machining the end of a workpiece with an end mill is that the lateral force imparted to the end mill during the machining operation deflects or bends the end mill outwardly away from the workpiece. Consequently, the machined surface is not perfectly flat and vertical as desired. Furthermore, since the tool bit is subjected to a lateral force and lateral bending with respect to its axis of rotation, the milling cutter frequently breaks during the end milling operation and can injure workmen in the area around the vertical mill. This is particularly true when relatively deep cuts are taken during an end milling operation.
A still further disadvantage of the previously known end milling operations is that the end milling operation leaves "chatter" marks along the machine side of the workpiece. These chatter marks are caused by deflection of the cutter. For many types of work pieces, such chatter marks are unacceptable.